The current harmonic pollution is increasingly serious and active power filter get the outside world wide concern due to its real-time harmonic suppression.The quality of harmonic current detection has a great influence on the active power filter.In this article

the present several kinds of harmonic detection methods based on Fourier transformation

transient reactive power theory

synchronous reference coordinate system theory

frequency domain analysis based on analog bandpass or bandstop

the sample and holding principle

Fryze time domain analysis

wavelet transformation

Prony/Kalman estimation

neural networks/adaptive filtering theory are summarized

compared and analyzed.